This invention relates to a process for applying a polymeric film to a fixed substrate and an apparatus suitable for performing this process. In a preferred embodiment, this invention relates to an apparatus for applying an extruded polymeric film to a roof as a sealing membrane.
Built-up roofing has long been used as a means of providing sealing membranes for roofs. Typically, built-up roofing is applied by applying alternating layers of felt and hot bitumen, and sealing the membrane with an additional layer of mopped hot bitumen. Three layers of felt are typically utilized. A layer of gravel or other aggregate is then laid on top of the bitumen to protect the membrane from environmental effects such as wind and sunlight, and to improve the appearance of the roof. Built-up roofing is heavy, and the application of the roof is labor intensive and and therefore relatively expensive to install.
Because of the shortcomings of built-up roofing, prefabricated roll roofing material has been developed. Commonly used prefabricated roll roofing material are fabricated from bitumen modified with atactic polypropylene ("APP"), bitumen modified with styrene-butadiene rubber, ethylene-propylene copolymer modified asphalt and vulcanized EPDM. These materials are usually reinforced with mats made of fabric, fiberglass or polyester. The rolls are usually "dusted" with sand or talc, or a release paper is applied to prevent the material from fusing together during storage. Shortcomings of these systems include poor adhesion to the roof and adjacent prefabricated roll roofing material and the need to remove the talc, sand or release paper before installation. Further, although labor required to install these prefabricated roof materials is not as great as built-up roofing a system which could be installed using less labor is desirable.
Prefabricated membranes are held in place by using an adhesive, mechanically fastening to the roof or by ballast. Application of adhesives is labor intensive and slow. Mechanically fastening the roofing material results in concentrated stress due to differential thermal expansion and movement of the roof. These concentrated stresses can result in tears which then allow water intrusion. Ballast is heavy and is subject to being moved by wind and foot traffic.
Another method of holding in place prefabricated roofing material involves using oxidized bitumen as an adhesive. This method is commonly used with styrene-butadiene rubber modified bitumen roll roofing material. The oxidized bitumen is melted and spread using an industrial mop. Variations is the thickness of the mopped layer, the temperature of the oxidized bitumen when it is applied and the chemical consistency of the asphalt result in variations in the adhesion. Transporting the molten oxidized bitumen to the roof is also difficult.
Prefabricated roll roofing made from APP modified bitumen is typically held in place by "welding" the compositions to the substrate and adjacent roofing material by partially melting the roll. Partially melting the roll roofing material is often accomplished using an open flame. Welding is difficult if not impossible to accomplish evenly, resulting in flaws which can allow water intrusion. The use of an open flame with the roll roofing material, which is itself flammable, is hazardous and has been the cause of many serious structural fires.
An apparatus intended to unroll, heat, and press into place rolled roofing is described in U.S. Pat. No. 4,761,201. In this apparatus, a series of burners is positioned in a frame, with each burner pointing toward a roll of roofing material which is capable of heating the roll of roofing material. The frame supports the burners and the roll of roofing material so that the roll may be unrolled with the full weight of the roll pressing the heated roll onto the roof substrate. The apparatus includes a manually adjustable pivoted bracket to hold the burners at a predetermined distance from the roll of roofing material. This is necessary due to the decreasing diameter of the roll as it is unrolled. Although this apparatus provides a means to apply rolls of roofing material, many shortcomings are evident. The manual adjustment of the distance from the burners to the roll is subject to human error, and even if operated flawlessly, the evenness of the heating is also dependent on the evenness of the rate that the apparatus is moved across the substrate. The apparatus also requires that open flames be directed at the roll of roofing material, which is is vary undesirable, as discussed above.
The optimum composition and thickness of a sealing membrane for a roof will vary according to the amount of insulation under the roof, the roof's slope, local climate, ambient conditions at the time of application, exposure to sunlight, exposure to wind, desired color and appearance and several other such factors. Prefabricated rolls of roofing material cannot be made in such a variety of compositions that a near optimum roof system can be applied consistently. A system for applying water proof membranes which allows for adjustments for some or all of these conditions is not currently available.
Membranes similar to roof membranes are utilized in other applications. For example, stress absorbing membrane interlayers are applied between layers of road materials to prevent cracks caused by differential expansion of the layers. Rolled membranes of bituminous material on polyester reinforcement mats are often used in these applications, and suffer from many of the shortcomings described above for roofing materials.
It is therefore an object of the present invention to provide a process to apply a sealing membrane to a fixed substrate wherein the thickness of the membrane is determined in-situ, wherein an open flame is not required at the point of application for application of the sealing membrane to the fixed substrate and wherein hot bitumen is not required as an adhesive. In a preferred embodiment of the present invention, it is an object to provide a process to apply a sealing membrane to a fixed substrate wherein the composition can be determined in-situ. In another aspect, it is an objective of this invention to provide an apparatus capable of performing the process described above.